Wireless-telegraph receiver



May 22, 1923. r 1,455,896

L. B.v TURNER I WIRELESS TELEGRAPH RECEIVER Filed Feb. 9, 1921 PatentedMay 22, 1923.-

UNITED STATES 1,455,896 PATENT OFFICE.

LAURENCE BEDDO METURNEB, OF CAMBRIDGE, ENGLAND.

WIRELESS-TELEGRAPH RECEIVER; I

Application filed February 9,1921. 'Serial No. 448,688.

telegraphy with long waves and with receiving circuits of small damping,limitation of speed is imposed by the slowness with which theoscillation produced in the receiving circuit during a dot or dash ofthe signalling code dies away during the subsequent space of thesignalling code. The rate of dying away is increased if the damping isincreased; but the amplitude reached is then decreased, which implies adecrease in the sensitiveness of the receiver.

The present invention consists in the provision of means whereby thereceived signal (dot on dash, in the Morse code), upon reaching anamplitude competent to. operate the receiving instrument, introducesadditional damping into the receiving circuit; which additional dampingis maintained as long as the incoming signal is maintained butautomatically disappears, or substanti'ally disappears during the nextspacing period. The automatic increasing of the damping is hereinafterreferred to as curbing; and curbing is said to begin when the additionaldamping is first introduced, and to end when it is removed. The curbingis preferably maintained throughout as large a proportion of the spacingperiod as possible. Under these conditions, the decrement of theuncurbed receiving circuit may be made small, thus favouring the growthof the oscillation in the receiving circuit up to its operativeamplitude; the curbing thereupon efl'ected imposes a restriction on thefurther growth of amplitude; and, if the curbing is maintained for atime after the cessation of the incoming signal, the rate at which theamplitude dies away towards zero is greater than that corresponding tothe decrement of the uncurbed circuit.

Curbing may be effected in all or any of the receiving circuits,including the antenna circuit itself; but the arrangement preferred isone in which the antenna is relatively highly damped, and has coupled toit a circuit .of specially low decrement to which the curbing isapplied. The low decrement of the uncurbed receiving circuit may bearrived at in any known way, with or without the aid of retroactivethermionic triode circuits associated with the receiving circuit for thepurpose of reducing its decrement in the well known manner.

One way of curbing the oscillatory receivlng circuit is to cause thereceived oscillalawn to deflect the tongue of a relay which, in thespacing position, short-circuits a resistance comprised in theoscillatory circuit, 7

but ceases to do so when deflected into the marking position. The relaymay be made somewhat sluggish of return'to the spacing position, so asto prolong the duration of the marking contact,'and to maintain thecurbmg during part of the spacing period; and mechanical or electricaldevices may be used to maintain the curbing for a while after the tongueof the relay has returned to the spacing position.

Alternatively, the tongue of the relay may control the grid or anodepotential, and

thereby the anode-anode slope conductance, of a thermionic triodeconnected to the receiying circuit in such a way as to produce in 1tmore or less damping according to the value of the said anode-anodeslope conductance. If the relay controls the anode potential of thethermionic tube, the grid may be dispensed with, and a diode or Flemingvalve may be substituted for the triode.

The relay may be of any pattern, and may be actuated by the receivedoscillation in any way, with or without intermediate amplifiers.

The invention is more particularly described by reference to thefollowing figures, which illustrateparticular methods of-putting it intoeffect. Figure 1 shows anarrangement in which resistance is switchedinto and out of the receiving oscillatory circuit by a relay directly;and Figure 2 shows one method of effecting the curbing by anintermediary thermionic tube under control of the relay.

In both the figures, L is an inductance and .C is a condenser comprisedin the receiving the marking period of the incoming signal the decrementof LC- should be small; but in order that the oscillation may die downsufficiently rapidly when the incoming signal ceases, the quantity (R.T)/L must bekept sufficiently large, where R is the total effectiveresistance of the oscillatory circuit, and T is the duration of thespacing period at the speed of signalling in use.

In Figure 1, 5 is an additional resistance inserted in the LC circuit,and is wholly or gartially short-circuited when the relay is but is notshort-circuited when the relay is at M. Until the oscillation in LG hasbeen built up sufliciently to actuate 1, the decrement is small; butwhen 1 is deflected curbing begins. The value of theresistanceshort-c-ircuited by 1 is preferably made just great enough toprevent any substantial further growth of the oscillation after curbingbegins. Curbing continues until 1 returns from M to S, which event maybe more or less delayed after the termination of the incoming signal byadjusting the sluggishness of'the relay due to 4, as well as by theusual mechanical adjustments of the rela ln Figure 2, 6 is a thermionictriode, with filament 7, grid 8 and anode 9. 10 is the filament battery,and 11 the anode battery. The whole or part of L is inserted in theanode circuit 9, L, 11, 7. 12 is a battery tending to maintain the gridat-a potential (-E with respect to the filament. 13 is a high resistanceinterposed between 12 and 7 and shunted by a condenser 14:. 15 is abattery of electromotive force E and is so connected, through the tongueand the M contact of the relay, across 13a'nd 14 as to raise the gridpotential to the vvalue (E E when the relay ,is deflected to M. When therelay returns to S, the potential of 8 falls gradually at a ratedetermined by the time-constant of 13, 14, and would finally again reach(-E).

It is well known that when the grid potential is sufliciently low, theanode-anode slope conductance is extremely low. in which condition 6might introduce negligible damping into the oscillatory circuit; andthat when the grid potential is raised to a suitable value, theanode-anode slope conductance rises to some relatively very high value,in which condition 6 introduces more or less damping into theoscillatory circuit as more r less of L is included in the anodecircuit. The anode-anode slope conductance is approximately constantover a considerable range of grid otential, and (E -E is preferably ma eto lie near the upper end of this range; while E is preferably givensuch a large value as to make the anodeanode slope conductance sensiblyzero before curbing occurs. When the relay is at M, the oscillatorycircuit is curbed by 6, and remainscurbed after the relay leaves M untilthe grid potential has fallen to a considerably lower value. The rate offall, and therefore the duration of curbing after the relay leaves M, iscontrolled by ad usting the product of the resistance of 13 and thecapacity of 14.

The adjustment is preferably made so as to cause curbing to continue aslong as possible during the spacing period of the incoming signal.

The amount of additional damping introduced may be chosen to suitspecial conditions; but with undamped incoming signals it will generallybe convenient to make the decrement of the oscillatory circuit duringcurbing as great as possible, namely, of the value which would gave anamplitude oi oscillation under a continued signal equal to the operativeamplitude. During curbing the current then remains constant at theoperative value untilthe incoming signal ceases, whereu on it falls withthe greatest possible rapidity.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is 1. Apparatus foruse in wireless telegraphy,comprising an oscillatory receiving circuit of relatively low decrement,a connection including a relay joined to the oscillatory circuit andmeans operated by said relay for increasing automatically the decrementof the oscillatory circuit when the amplitude of the current thereinreaches the operative value.

2. Apparatus for use in wireless telegraphy, comprising an oscillatoryreceiving circuit of relatively low decrement, a connection including arectifier and a relay joined to the oscillatory circuit and meansoperated by said relay for increasing automatically the decrement of theoscillatory circuit when the amplitude of the current therein reachesthe operative value.

3. Apparatus for use in wireless telegraphy, comprising an oscillatoryreceiving circuit of relatively low decrement, a connection including arelay joined to the oscillatory circuit and means operated by said relayfor increasing automatically the decrement of the oscillatory circuitwhen the amplitude thereof reaches the operative value, said means beingadapted to retain the increased decrement during the spacing periodfollowing the signal.

' of the 1,455,sae

. 4. Apparatus for use in wireless telegraphy comprising an oscillatoryreceiving circuit of relatively low decrement, a connec-- tion includinga relay, joined to the oscillatory circuit, and a thermionic tube withconnections coupling it to the oscillatory circuit and means forcontrolling the potential rid of the thermionic tube'by the relay wereby additional decrement is applied to the oscillatory circuit.

5. Apparatus for use in wireless telegraphy comprising an oscillatoryreceiving circuit, a connection including a relayjoined to theoscillatory circuit, a condenser and a resistance, shunting the relay,and means controlled by the relay for applying addi tional decrement tothe oscillatory receiving circuit.

. 6. Apparatus for use in wireless telegraphy comprising an oscillatoryreceiving circuit including an inductance and a condenser, a connectionincluding a relay, joined across the condenser to the oscillatoryreceiving circuit, a thermionic tube, means connecting the anode circuitof said thermionic tube to the inductance, means for controlling thepotential of the grid of said thermionic tube by the relay, said meansin- "eluding a battery adapted in one position of resistance andcondenser being in parallel with said battery when the battery circuitis closed by the relay.

Receiving apparatus for wireless telegraphy comprising an oscillatoryreceiving circuit of relatively low decrement and means responsive'tothe magnitude of currents in said receiving circuit for materiallyincreasing automatically the decrement of said oscillatory circuit.

8. Apparatus for use in wireless telegraphy comprising an oscillatoryreceiving circuit of relatively low decrement, a relay,

connectionsbetween said receiving circuit' and said relay whereby saidrelay receives a current the magnitude of which increases withthevmagnitude of the current in said receiving circuit and meansoperated by said relay for increasing automatically the decrement of theoscillatory circuit when .the amplitude of the current therein attains apredetermined value.

. LAURENCE BEDDOME TURNER.

